cup_edit/lib/animations/bvh.dart

import 'dart:io';
import 'dart:math';
import 'dart:ui';
import 'package:flutter_filament/animations/animation_data.dart';
import 'package:vector_math/vector_math_64.dart';

enum RotationMode { ZYX, XYZ }

enum Axes { Filament, Blender }

Map<RotationMode, Matrix3> _permutations = {
  RotationMode.XYZ: Matrix3.identity()
  // RotationMode.ZYX:Matrix3.columns([],[],[]),
};

class BVHParser {
  static Map<String, String> parseARPRemap(String arpRemapData) {
    final remap = <String, String>{};
    var data = arpRemapData.split("\n");
    for (int i = 0; i < data.length;) {
      var srcBone = data[i].split("%")[0];
      if (srcBone.isNotEmpty && srcBone != "None") {
        var targetBone = data[i + 1].trim();
        remap[targetBone] = srcBone;
      }
      i += 5;
    }
    return remap;
  }

  static BoneAnimationData parse(String data, List<String> meshNames,
      {Map<String, String>? remap,
      RegExp? boneRegex,
      RotationMode rotationMode = RotationMode.ZYX,
      Vector3? rootTranslationOffset,
      axes = Axes.Filament}) {
    // parse the list/hierarchy of bones
    final bones = <String>[];
    double frameLengthInMs = 0.0;
    var iter = data.split("\n").iterator;
    while (iter.moveNext()) {
      final line = iter.current.trim();
      if (line.startsWith('ROOT') || line.startsWith('JOINT')) {
        var bone = line.split(' ')[1];
        if (remap?.containsKey(bone) == true) {
          print("Remapping $bone to ${remap![bone]!}");
          bone = remap![bone]!;
        }
        bones.add(bone);
      } else if (line.startsWith('Frame Time:')) {
        var frameTime = line.split(' ').last.trim();
        frameLengthInMs =
            double.parse(frameTime) * 1000; // Convert to milliseconds
        print("Got frame time $frameTime frameLengthInMs $frameLengthInMs");
        break;
      }
    }

    // filter out any bones that don't match the regexp (if provided)
    final boneIndices = boneRegex == null
        ? List<int>.generate(bones.length, (index) => index)
        : bones.indexed
            .where((bone) => boneRegex.hasMatch(bone.$2))
            .map((bone) => bone.$1);

    // the remaining lines contain the actual animation data
    // we assume the first six are LOCX LOCY LOCZ ROTZ ROTY ROTX for the root bone, then ROTZ ROTY ROTX for the remainder
    final translationData = <List<Vector3>>[];
    final rotationData = <List<Quaternion>>[];
    while (iter.moveNext()) {
      final line = iter.current;
      if (line.isEmpty) {
        break;
      }
      var parseResult = _parseFrameData(line,
          axes: axes, rootTranslationOffset: rootTranslationOffset);

      rotationData.add(
          boneIndices.map((idx) => parseResult.rotationData[idx]).toList());
      translationData.add(<Vector3>[parseResult.translationData] +
          List<Vector3>.filled(bones.length - 1, Vector3.zero()));
    }

    return BoneAnimationData(boneIndices.map((idx) => bones[idx]).toList(),
        meshNames, rotationData, translationData, frameLengthInMs,
        isModelSpace: true);
  }

  static ({List<Quaternion> rotationData, Vector3 translationData})
      _parseFrameData(String frameLine,
          {Vector3? rootTranslationOffset, axes = Axes.Filament}) {
    final frameValues = <double>[];
    for (final entry in frameLine.split(RegExp(r'\s+'))) {
      if (entry.isNotEmpty) {
        frameValues.add(double.parse(entry));
      }
    }
    // first 3 values are root node position (translation), remainder are ZYX rotatons
    // this is hardcoded assumption for BVH files generated by momask only; won't work for any other animations in general

    // Blender exports BVH using same coordinate system (i.e. Z is up, Y points into screen)
    // but Filament uses Y-up/Z forward
    late Vector3 rootTranslation;
    late Vector3 Z, Y, X;
    if (axes == Axes.Blender) {
      rootTranslation =
          Vector3(frameValues[0], frameValues[2], -frameValues[1]);
      Z = Vector3(0, 1, 0);
      Y = Vector3(0, 0, -1);
      X = Vector3(1, 0, 0);
    } else {
      rootTranslation = Vector3(
        frameValues[0],
        frameValues[1],
        frameValues[2],
      );
      Z = Vector3(0, 0, 1);
      Y = Vector3(0, 1, 0);
      X = Vector3(1, 0, 0);
    }
    if (rootTranslationOffset != null) {
      rootTranslation -= rootTranslationOffset;
    }

    List<Quaternion> frameData = [];
    for (int i = 3; i < frameValues.length; i += 3) {
      var raw = frameValues.sublist(i, i + 3);
      var z = Quaternion.axisAngle(Z, radians(raw[0]));
      var y = Quaternion.axisAngle(Y, radians(raw[1]));
      var x = Quaternion.axisAngle(X, radians(raw[2]));
      var rotation = z * y * x;

      frameData.add(rotation.normalized());
    }
    return (rotationData: frameData, translationData: rootTranslation);
  }

  static double radians(double degrees) => degrees * (pi / 180.0);
}